# Static frequency converter

Canonical URL: https://eloragrid.ai/symbols/static-frequency-converter
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: SFC
Drawing use: SLD
Reference families: IEC, IEEE / ANSI

A rectifier and inverter in one unit that converts AC at one frequency to AC at another, such as 50 Hz to 60 Hz.

## In plain English

### What does Static frequency converter mean?

A static frequency converter rectifies the incoming AC to DC and inverts it back to AC at a different frequency and often a different voltage. It is used to supply 60 Hz equipment from a 50 Hz network, to provide shore power to ships, to feed 400 Hz aircraft supplies and to link microgrids or networks running at different frequencies.

### A simple example

Drawings show a converter box with AC marks on both sides and the frequencies noted, or two converter boxes back to back with a DC link between them. Input and output transformers are often drawn to provide isolation and voltage matching.

### What the drawings help you do

The output is converter-sourced, so fault current is limited and selective protection downstream must be checked. The symbol does not show overload capability or whether the output can supply motor starting current.

### This particular reference

A rectifier and inverter in one unit that converts AC at one frequency to AC at another, such as 50 Hz to 60 Hz. A static frequency converter changes frequency electronically; a motor-generator set does the same with rotating machines.

### Terms

- DC: Direct current: electricity flowing in one direction.
- AC: Alternating current: electricity whose direction changes periodically.
- Winding: A coil of conductor inside an electrical machine or transformer.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)
- [Bidirectional three-/single-phase AC/DC PFC and inverter application note](https://www.infineon.com/assets/row/public/documents/24/42/infineon-ac-dc-pfc-11-kw-high-efficiency-high-density-bidirectional-three-single-phase-inverter-applicationnotes-en.pdf)


## What it represents

A static frequency converter rectifies the incoming AC to DC and inverts it back to AC at a different frequency and often a different voltage. It is used to supply 60 Hz equipment from a 50 Hz network, to provide shore power to ships, to feed 400 Hz aircraft supplies and to link microgrids or networks running at different frequencies.
Drawings show a converter box with AC marks on both sides and the frequencies noted, or two converter boxes back to back with a DC link between them. Input and output transformers are often drawn to provide isolation and voltage matching.
The output is converter-sourced, so fault current is limited and selective protection downstream must be checked. The symbol does not show overload capability or whether the output can supply motor starting current.

## How to read it

- Read both the input and output frequency labels.
- Check output short-circuit capability for downstream protection.

## Information to show or reference

- State input and output voltage and frequency.
- Show isolation transformers.
- Reference overload and fault capability.

## Important distinction

A static frequency converter changes frequency electronically; a motor-generator set does the same with rotating machines.

## Facts

- Conversion: AC to DC to AC
- Typical use: 50/60 Hz and 400 Hz supplies
- Fault current: Converter-limited
- Preview: Independent educational illustration; consult the applicable standard and project legend for the exact graphic

## Public references

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC graphical symbol context for converters.
- [Bidirectional three-/single-phase AC/DC PFC and inverter application note](https://www.infineon.com/assets/row/public/documents/24/42/infineon-ac-dc-pfc-11-kw-high-efficiency-high-density-bidirectional-three-single-phase-inverter-applicationnotes-en.pdf) — Infineon Technologies. Public AC/DC and inverter stage context.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.